An outline structure of a gas turbine moving blade is shown in FIG. 4. In this drawing, the gas turbine moving blade 1 includes a blade part 3 forming a blade, a platform 5 connected to a bottom of the blade part 3, and a shank part 7 located below the platform 5, where a blade root part 9 is formed below the shank part 7.
Then, in FIG. 4, a continuous groove having a wave shape is formed in both side walls of the blade root part 9. A continuous groove having the same shape is formed in a rotor disk 11. By allowing the groove of the blade root part 9 to engage with the groove of the rotor disk 11, the gas turbine moving blade 1 is fixed to the rotor disk 11. Then, in the same fixing manner, a plurality of gas turbine moving blades 1 is adjacently fixed to the rotor disk 11 in a circumferential direction.
Additionally, a cavity 13 is formed by a lower surface of the platform 5 and a side surface of the shank part 7 of the gas turbine moving blade 1, and sealing air is supplied from the rotor to the cavity 13, thereby preventing high-temperature combustion gas from leaking from a gap 15 between the adjacent platforms 5 and 5 by the use of the sealing air.
In the structure of the gas turbine moving blade 1 having the above-described configuration, since the blade part 3 is exposed to the high-temperature combustion gas, at least one moving blade cooling passageway 17 is provided in the inside of the blade part 3 in order to cool the blade part 3, and the moving blade cooling passageways 17 introduces cooling air from the blade root part 9. Although it is not shown in the drawing, a part or a whole part of the passageway communicates with each other so as to form a serpentine cooling passageway and to cool the whole part of the blade part 3.
Additionally, a part of the cooling air introduced into the moving blade cooling passageways 17 is discharged from the trailing edge of the blade part 3 so as to further cool the trailing edge of the blade part 3.
Since the cooling air supplied to the moving blade cooling passageways 17 is used to cool the blade part 3, the cooling air is controlled at a high-pressure different from the sealing air, and is cooled before supplying if necessary.
Additionally, since the surface of the platform 5 is exposed to high-temperature combustion gas, in order to prevent a thermal damage and a crack caused by thermal stress, there are proposed various structures for cooling the platform 5.
For example, a platform 010 of a gas turbine moving blade disclosed in Patent Document 1 (Japanese Patent Application Laid-Open No. H10-238302) is shown in FIG. 5. FIG. 5(a) is a longitudinal sectional view showing the gas turbine moving blade and FIG. 5(b) is a sectional view taken along the line E-E shown in FIG. 5(a). Patent Document 1 discloses a technique for cooling an upper surface of the platform 010 by the use of sealing air 012 flowing to a lower surface of the platform 010. A plurality of sealing air passageway holes 015 is perforated in the inside of the platform 010 on a concave side 013 so as to be formed through the platform 010 in a radial direction relatively from a center of a turbine shaft.
Additionally, a convection cooling hole 017 relatively extends in an oblique manner from the center of the turbine shaft in a radial direction so as to be opened at the upper surface of the platform 010. The opening formed in the upper surface of the platform 010 is provided with a shaped film discharge hole of which an end is widened so as to cool the upper surface of the platform 010 by the cooling air flowing and extending on the upper surface of the platform 010 crawlingly.
Then, a structure for improving a cooling performance of a gas turbine moving blade disclosed in Patent Document 2 (Japanese Patent Application Laid-Open No. H11-247609) is shown in FIG. 6. FIG. 6(a) is a top view showing the gas turbine moving blade and FIG. 6(b) is a sectional view taken along the line F-F shown in FIG. 6(a). Patent Document 2 discloses a cooling passageway 026 which is formed through the inside of a platform 020 so that one ends communicate with a cooling passageway 024 for cooling the inside of the moving blade 022 and the other ends are opened at both end surfaces of the platform 020.
Further, as shown in FIG. 7, Patent Document 3 (Japanese Patent Application Laid-Open No. 2006-329183) discloses a structure for cooling a portion in the vicinity of a front end of a platform 052 in such a manner that a cover plate 050 is attached between a lower surface of a platform 052 and a shank 054 so as to form a space 056 by the cover plate 050, high-pressure cooling air is guided from a cooling passageway 058 for cooling the inside of a moving blade to the space 056 via a passageway 059, and then the high-pressure cooling air is supplied to the surface of the platform 052 via the space 056 and cooling holes 061 and 063.
As described above, various techniques for cooling the platform of the gas turbine moving blade have been proposed. Patent Document 1 discloses the structure for cooling the platform 010 by the use of the sealing air 012. However, since the sealing air is supplied from the lower surface of the platform in order to prevent the high-temperature combustion gas from leaking from a gap between the adjacent platforms to the rotor, in general, a temperature of the sealing air is not controlled and moreover, a pressure of the sealing air is not controlled at high pressure. As a result, it is not possible to obtain the sufficient cooling performance just by cooling the platform by the use of the sealing air.
Particularly, since a portion in the vicinity of the side edge of the platform away from the bottom of the blade is away from the moving blade cooling passageway 019 for cooling the inside of the blade, it is difficult to cool the portion. Due to such a thermal condition, a cooling structure is required which is capable of effectively cooling the portion in the vicinity of the side edge of the platform away from the bottom of the blade, that is, the surface exposed to the high-temperature combustion gas.
Meanwhile, Patent Documents 2 and 3 disclose the structure for cooling the platform by the use of the high-pressure cooling air flowing to the moving blade cooling passageway instead of the sealing air.
However, in Patent Document 2, the cooling air is discharged from the cooling passageway 026, which is formed through the inside of the platform 020 so that one ends communicate with the cooling passageway 024 for cooling the inside of the moving blade 022 and the other ends are opened at both end surfaces of the platform 020, to the end surfaces of the platform 020, that is, the gap between the adjacent platforms. For this reason, it is possible to cool and seal the end surface of the platform 020, but a problem arises in that it is not possible to effectively cool the upper surface of the platform in the vicinity of the side end portion exposed to the high-temperature combustion gas.
Then, in Patent Document 3, the cooling air flowing to the moving blade cooling passageway is guided from the side end portion of the platform to the upper surface of the platform. However, since the space is formed by attaching the cover plate between the shank and the lower surface of the platform, and the cooling air is discharged to the surface in the vicinity of the front end portion via the space, it is necessary to fix the cover plate to the platform and the shank by welding or the like. As a result, a problem arises in that the processes of assembling increase. Also, since the moving blade rotating at a high speed needs to have higher reliability than that of a stationary member, it is necessary to remove an additional member such as the cover plate as much as possible in general.